Ok this is to Import /export your gmail calendar to the native calendar that comes with the n900

It is not an automated solution just the one that works for me. As with anything YMMV. I am still having a little trouble getting events made on the 900 to import to gmail correctly.

From gmail calendar to n900

In the n900 opening an ical link in gmail calendar for your specific calendar will bring up a dialog to import the calendar.

Step by step

Method 1
Open a web browser and log into your google calendar.
On the left there is a box displaying your calendars. Choose settings
Choose the calendar you would like to import.
Choose the private ical link at the bottom. Click on the big blue link. A new page will open and a file download dialog will open. Choose "Open with Calendar"
Select the calendar that you would like to import to. Choose save.

Method 2
I have my gmail account set up on the n900, so I sent myself an email with the ical links to my Google calendars. I then opened up the email on the device and just clicked the link.
A new page will open and a file download dialog will open. Choose "Open with Calendar"
Select the calendar that you would like to import to. Choose save.

From n900 to Google calendar

Not perfect sync.

Open calendar on n900 select the calendar toolbar. Choose settings.
Choose edit calendar.
Choose the calendar to export.
Choose "export" dialog.
Save the file somewhere where you know it will be.
Open your Google calendar in a web browser.
On the left there is a box displaying your calendars. Choose settings.
Choose import calendar. In the dialog choose browse. Navigate to you save file. Select calendar you would like to import to and then select import.

Good luck to all.

E.